Multiparametric MRI of Neurodegeneration in the Peripheral Nervous System
The overall goal of this dissertation is to develop and evaluate magnetic resonance imaging (MRI) methods to characterize peripheral nerve microstructure and pathologies in vivo in humans. More specifically, we assessed the ability of quantitative MRI methods developed for the central nervous system (CNS) to assay myelin and axonal pathologies in peripheral nerves in patients with inherited neuropathies and nerve trauma. Furthermore, we translated a recently developed advanced diffusion MRI method to the peripheral nervous system for the first time to overcome the lack of specificity inherent in traditional diffusion MRI approaches. Of the two pathologies studied, both have limitations in standard clinical care that may be augmented by noninvasive measures of nerve pathology that can be assessed with MRI methods. Despite this promise, many of quantitative MRI methods have not been translated to the peripheral nervous system (PNS) because of the technical challenges associated with imaging small nerves. In this work, we developed strategies to overcome these challenges, evaluated these new methods in two patient cohorts, and translated an emerging diffusion method that may improve our ability to differentiate myelin and axon pathologies. If successful, the methods herein could be used to improve clinical care by providing information about the degree of pathology, which can inform clinicians and surgeons of proper treatment strategies (e.g., the need to re-operate) and response to therapy.